<template>
  <section id="app">
    <!-- 输入框 -->
    <header class="header">
      <h1>小黑记事本</h1>
      <input v-model="todoName" placeholder="请输入任务" class="new-todo" />
      <button @click="add" class="add">添加任务</button>
    </header>
    <!-- 列表区域 -->
    <section class="main">
      <ul class="todo-list">
        <li class="todo" v-for="(item, index) in list" :key="item.id">
          <div class="view">
            <span class="index">{{ index + 1 }}.</span> <label>{{ item.name }}</label>
            <button @click="del(item.id)" class="destroy"></button>
          </div>
        </li>
      </ul>
    </section>
    <!-- 统计和清空→ 如果没有任务，底部隐藏掉→ v-show -->
    <footer class="footer" v-show="list.length > 0">
      <!-- 统计 -->
      <span class="todo-count">合 计:<strong> {{ list.length }} </strong></span>
      <!-- 清空 -->
      <button @click="clear" class="clear-completed">
        清空任务
      </button>
    </footer>
  </section>
</template>

<script>
export default {
  data() {
    return {
      todoName: '',
      list: [
        { id: 1, name: '跑步1公里' },
        { id: 2, name: '跑步2公里' },
        { id: 3, name: '跑步5公里' },
      ]
    }
  },
  methods: {
    del(id) {
      // console.log(id);
      this.list = this.list.filter(item => item.id !== id)
    },
    add() {
      if (this.todoName.trim() === '') {
        alert('请输入任务名称')
        return
      }
      this.list.unshift({
        id: +new Date(),
        name: this.todoName
      })
      this.todoName = ''
    },
    clear() {
      this.list = []
    }
  }
}

</script>